Studies will be carried out to determine which features of the steroid molecule are required to inhibit sterol synthesis, with emphasis upon the inhibitory potencies of various metabolic precursors of cholesterol. The nature and functions of cytosolic receptors for inhibitory and non-inhibitory sterols will be investigated. The relationship between sterol synthesis and cell proliferation will be studied in 3T3 cell cultures and in virus-transformed 3T3 cells. The effects of administering inhibitory sterols (i.e., 25-hydroxycholesterol and 7-ketocholesterol) to normal and tumor-bearing mice will be investigated. The regulation of dolichol synthesis in cultured cells by HMG-CoA reductase will be examined.